Ground condition concerns have been overcome on a tunnelling scheme in Ohio, US using a tunnel boring machine (TBM) capable of operating in both earth pressure balance and hard rock single shield modes.
The Akron Ohio Canal Interceptor Tunnel has been delivered by a joint venture of Kenny Construction and Obayashi using a Robbins Crossover XRE TBM named Rosie after the iconic World War 2 image of Rosie the Riveter.
The new 1.89km tunnel will provide conveyance and storage to control combined sewer overflows in the city centre of Akron in Ohio. City of Akron mayor Daniel Horrigan described the project as the largest public improvement project in the city’s history and said it was a significant investment in the environment and infrastructure.
“One of the most challenging aspects of this job was that we launched right into the most difficult part,” said Kenny Construction project manager David Chastka. “We had 60m of soft ground, a very short reach, and then from there we went right into a mixed face for 180m.
“It took everybody we had in the industry, everybody from Robbins, to fight through that first 240m.”
The TBM was designed for the project’s geology, which transitioned from soil to partial face shale to full face shale rock. While in soft ground and mixed face conditions the machine operated in closed mode, but once it hit solid rock crews switched excavation to open mode.
“The TBM had the power to get to the other side and made advance rates we never thought we were going to get. It was very successful in hard rock,” said Chastka.
Advance rates once in full-face shale rock reached a high of 34m in one day with two 10-hour shifts.
Work is now under way to dismantled and lift the TBM from a reception shaft.